POEM 95: Support user/developer defined callback functions

[A-CGray]

No description provided.

[naylor-b]

@A-CGray are you familiar with OpenMDAO's 'hook' system? It's used by our report system, but it can also be used directly. It allows you to register functions either before or after (or both) a specific method in an OpenMDAO object, for example a Problem. So doing something like:

_register_hook('run_model', class_name='Problem', post=my_hook_function)

would call my_hook_function(p), where p is a Problem instance, at the end of the run_model method.

It's not very well documented, but if you're interested, take a look in openmdao/utils/hooks.py.

[A-CGray]

Thanks @naylor-b that does sound like it'd address the problem and driver level callbacks. Does it work at the component/system level too? i.e could the developer of a component implement a hook that will be called once at the end of run_model regardless of how the end user uses that component in their model? And without the user having to call _register_hook? If so then I think this would solve our problems

[naylor-b]

The use case where the component is registering hooks on the problem or driver might be hard to do in a non-hacky way. We may need to add something more specific for that instead of using the existing hook system.